This invention relates generally to vehicle wheel service systems and more particularly, to methods and systems for operation of vehicle wheel service systems such as wheel balancers and tire changers configured with machine vision sensors to measure a wheel assembly, to guide an operator during placement of imbalance correction weights, and to confirm correct placement of the imbalance correction weights on the wheel rim after installation.
At least some known vehicle wheel balancers are capable of optically scanning a vehicle wheel assembly consisting of at least a wheel rim mounted to a spindle shaft for rotation about an axis. A surface on the wheel assembly is sensed by means of a light beam such as a laser emitted by a light source, illuminating a single point on the surface of the wheel assembly, such that reflected light is received by a position-sensitive receiver. The spacing of the sensed surface or location relative to a reference point is then measured from the directions of the emitted and reflected light beams. In some systems, an actuator causes synchronous pivotal movement of the light source and the receiver about a common pivot axis, and the measurement values of the receiver are fed to an electronic evaluation system to ascertain the sensed location on the vehicle wheel from a reference location. By positioning the light source and the receiver together facing towards various positions on the wheel rim, a contour of the wheel rim, and in particular an internal contour of the wheel rim, can be determined.
However, a scanning device that includes a plurality of moving parts, actuators, and bearings is prone to wear and misalignment requiring periodic maintenance, recalibration, and/or verification of proper operation, which is expensive and time-consuming. The time required for the scanned measurement can also be long, even longer than an imbalance measurement procedure, and longer than manually entering the dimensions using conventional electro-mechanical systems such as measurement arms.
Other known automotive wheel service systems utilize a planar light beam, such as a sheet of light, which is projected to impinge on a stripe-shaped impingement area on the surface of the wheel assembly. Light reflected from the stripe-shaped impingement area is received at an imaging sensor mounted outside of the projection plane, and processed to evaluate the shape of the illuminated stripe-shaped impingement area. Deviations in the shape of the illuminated stripe-shaped impingement area from a straight line, as seen by the imaging sensor, are interpreted as representations of the surface contour onto which the light is projected.
However, scanning devices that rely upon a projected planar light beam and observation of deviations in the resulting reflected light from a linear image require that the imaging sensor be positioned outside the plane of the projected light beam to provide the imaging sensor with a field of view sufficient to observe small deviations from a straight line in the reflected light resulting from small contours of the surface onto which the light is projected. These spacing requirements can be difficult to accommodate in compact vehicle service systems.
Independent of the means by which the data is acquired, vehicle wheel balancers utilize contour data to determine suitable axial placement locations for imbalance correction weights during an imbalance correction procedure. An operator may further identify to the system a desired axial placement location for an imbalance correction weight by pointing to the desired position with a finger or indicator wand, such as shown in U.S. Pat. No. 7,495,755 B2. Commonly, the process of installing imbalance correction weights is a manual process, requiring the operator to follow instructions for weight selection and proper placement provided by the vehicle wheel balancer in response to the measured imbalance of the wheel assembly. Depending upon the operator's level of skill, attentiveness, and attention to detail, the imbalance correction weights may not be installed precisely where indicated, leaving the wheel assembly with an unintended measure of residual imbalance. For example, when a vehicle wheel balancer directs placement of a first imbalance correction weight on an “inner correction plane” and a second imbalance correction weight on an “outer correction plane”, an inattentive operator may misplace the weights by installing an imbalance correction weight at the wrong correction plane.
Accordingly, it would be advantageous for automotive vehicle wheel balancers to utilize optical rim contour measurement components to provide data associated with a vehicle wheel assembly in addition to measuring rim profiles, to facilitate correct installation of imbalance correction weights by providing the operator with real-time visual cues as to the correct axial placement location of identified imbalance correction weights, and which can quickly identify, to an operator, incorrect placement locations and/or applied incorrect weight amounts (if the weight dimensions are known).